Latch devices for indexing tables and the like



Oct. 1, 1968 D. R. PATERSON 3,403,586

LATCH DEVICES FOR INDEXING TABLES AND THE LIKE 3 Sheets-Sheet 1 Filed March 21, 1966 III lllll II NIH Hll I Oct. 1, 1968 o. R. PATERSON 3,403,586

LATCH DEVICES FOR INDEXING TABLES AND THE LIKE File d March 21, 1966 s Sheets-Sheet 2 F'IG.3

Oct. 1, 1968 D. R. PATERSON 3,403,585

LATCH DEVICES FOR INDEXING TABLES AND THE LIKE s sheets-sheet 5 Filed March 21, 1966 FIGS United States Patent 3,403,586 LATCH DEVICES FOR INDEXING TABLES AND THE LIKE David R. Paterson, The Grange, Hemmingford Abbots, Huntingdon, England Filed Mar. 21, 1966, Ser. No. 536,059 4 Claims. (Cl. 74-820) ABSTRACT OF THE DISCLOSURE An indexing table rotatably mounted on a fixed support having a latching device for indexing the table which is pivotably mounted on the fixed support and which cooperates with a plurality of circumfe-rentially-arranged buttons projecting from the indexing table. The latch lever is notched to embrace any one of the buttons and is provided with two rollers mounted on each side of the notch to engage the particular button being acted upon.

This invention relates to latch devices for indexing tables and the like. The words indexing tables and the like are used to cover rotary indexing tables and other indexing supports for workpieces or tools used in connection with machine tools, and also rectilinearly movable tables or supports which are movable from one to another of several fixed positions, all of which are required to be held rigidly in any one of their indexed positions.

It has previously been proposed to employ slidable pins as latch devices, and, whilst the said pins could be provided with tapered ends entering tapered sockets in the tables to avoid increasing play with increasing wear, the pins were necessarily a sliding fit in guide bushes or the like, and wear between the pins and the bushes introduced play which was unavoidable. Another previously proposed arrangement was a pivoted latch arm having a notch to engage a pin or button fixed to the table or the like, but, with that arrangement, wear on the sides of the notch caused the development of play in a relatively short time.

It is the object of the present invention to provide an improved latch device in which initial play is completely eliminated and the device has a very long life before play has any tendency to develop.

According to the present invention, a latching device for an indexing table or the like comprises a pivoted latch lever mounted on a fixed support and co-operating with a plurality of buttons or like projections on the indexing table or the like, the latch lever being notched to embrace any one of the said projections and having two rollers mounted one on each side of the notch to engage the said projection, the spacing of the rollers being such that the distance between them is slightly less than the diameter of the projection, resulting in an interference contact between the said rollers and the projection when the latch is engaged.

Preferably, the latch arm is urged towards its engaged position by a spring or springs.

The spring or springs may act on the latch arm through a toggle mechanism and the said latch arm is disengaged by a Geneva mechanism associated with a power drive to the indexing table.

The invention is hereinafter described with reference to the accompanying drawings, in which:

FIGURE 1 is an inverted plan view of a rotating indexing table embodying a latching device according to the invention;

FIGURE 2 is a sectional elevation taken on the line 22 of FIGURE 1;

FIGURE 3 is a sectional elevation, on a larger scale, taken on the line 3--3 of FIGURE 1;

3,403,586 Patented Oct. 1, 1968 FIGURE 4 is a partial inverted plan view, with some parts omitted, showing the latching device; and

FIGURE 5 is a detail section on the line 5P5 of FIG- URE 1.

Referring to FIGURES 1 and 2 of the drawings, a circular table 10 (FIGURE 2) is rotatably mounted, by means of tapered roller bearings 11, on a stub shaft 12 fixedly mounted in a hollow cylindrical base 13 adapted to be mounted, by means of bolts entering holes 14 there in, on a bench or on the working surface of a machine tool. The table 10 is driven for indexing by a Geneva mechanism the star wheel 15 of which drives, through a friction clutch (not shown) a co-axial spur wheel 16 meshing with a spur wheel 17 on a lays'haft 18, the layshaft 18 also carrying a further spur wheel 19 which meshes with a spur wheel 21 secured to the underside of the table.

The driving member of the Geneva mechanism is a rotatable assembly 22 carrying the usual rollers to engage with the star wheel 15, the rollers to engage in the slots 23 of the star wheel being shown in dotted lines at 24 in FIGURE 1, and the rollers to engage the concave arcuate surfaces 26 of the star wheel being similarly shown at 27. The rotatable assembly 22 has gear teeth 28 on its periphery to be engaged by a spur gear (not shown) driven by an electric motor and mounted in the bench or working surface on which the indexing table is mounted.

The rotatable assembly 22 includes a twin-lobed edge cam 29, the shape of which is best seen in FIGURE 4.

On the under side of the table 10, at equal angular intervals depending on the number of indexing positions of the table, are mounted a plurality of buttons 30 (one of which is shown in FIGURE 2) each having mounted on it a hardened steel sleeve 31. These buttons co-operate with a two-armed latch lever 32 pivotally mounted at 33 on the base 13 and having a notch 34 in which one or other of the buttons 30 is engaged to latch the table 10 in an indexed position. The latch lever 32 has two arms, one arm 35 carrying a roller follower 36 engaging the cam 29. The other arm of the lever 32 is divided, as shown in FIGURE 3, into two portions 37 and 38, spaced apart in the direction of the pivot axis of the said lever, and connected rigidly one to the other by a bridge-piece 39. The portion 37 of the lever arms 37 and 38 is pivotally connected at 41 to one link 42 of a toggle, the other link 43 of which is pivoted to the base at 44. Tension springs 45 connected to the toggle link 43 and to the base 13 tend to straighten the toggle and so to move the latch lever 32 in a direction to engage the notch in the said latch lever with a button 30. The lever 32 is pivoted on a lug 46 integral with the base 13 and projecting between the portions 37 and 38 of the lever. A pivot pin 47, having oppositely tapered portions 48 and 49, engages a tapered bush 50 mounted in a hole in the lug 46, needle roller bearings 51 being mounted between cylindrical bearing surfaces 52, formed in holes in the two parts of the latch lever, and split internally tapered inner bearing races 54 mounted on the pin 47. The inner bearing races 54 are loaded by resilient pads 55 urging them axially along the tapered portions of the pin 47 in a direction such that they tend to be expanded to take up wear and prevent play from developing in the bearing. The pads 55 are carried by end caps 56 secured to the outer faces of the portions 37 and 38 of the latch lever.

The other portion 38 of the second arm of the latch lever is substantially D-shaped as shown in FIGURE 4, the notch 34 being formed in its straight side. Hardened steel rollers 57, mounted one on each side of the notch 34, have their peripheral edges projecting slightly into the notch, and are mounted on needle roller bearings 58 on parallel pins 59 carried by the lever arm. The spacing between the rollers 57 is slightly less than the diameter of the buttons 30, for example from 10 to 30 thousandths of an inch less, whilst the width of the notch itself is at least as great as the diameter of the buttons 30. A stop, not shown, is provided to limit the angular movement of the latch arm in the direction in which it is urged by the springs 45, the stop being so positioned that a line joining the centres of the rollers 57 just passes beyond the centre of a button 30 engaged in the notch, making the latch self-locking.

To enable the spacing of the rollers 57 to be adjusted, the D-shaped portion 38 of the second lever arm is formed with an opening 61 (FIGURE 4), from which a slit 62 extends to the curved edge of said portion. A bore 63 in the lever receives a slidable rod 64 one end of which abuts against a face of the slot, and a wedge member 65 (FIGURE movable in a transverse hole in the lever by means of a screw 66, acts through a ball 67 on the rod 64 to expand the slit 62 and thus distort the lever portion 38 to vary the width of the notch 34.

T he buttons 30 are clamped in position on the underside of the table by screws 68 engaging in retaining members 69 fitted in a T-shaped circumferential slot in the table. Plates 71, apertured to receive shanks 72 on the buttons 30 may be clamped against the underside of the table, and may each receive one or more additional screws extending into the retaining members to provide additional security. Guide pieces 73 (FIGURE 2) may be provided between the buttons to prevent the latch lever from moving outwardly at positions between the buttons 30.

To perform an indexing movement of the table 10, the electric motor is started, causing rotation of the driving assembly 22. The initial angular movement of the said driving assembly causes the follower roller 36 to ride up one lobe of the cam 29 and release the latch, after which a roller 24 engages in a slot 23 of the star wheel of the Geneva mechanism and rotates the table through the desired angle, the roller 36 in the meantime engaging a dwell portion of the cam 29. When the angular movement of the table is completed, the roller 36 rides down a fall portion of the cam 29 to re-engage the latch. The driving assembly 22 makes a half-revolution for each indexing movement of the table 10.

Electric switches 74 and 75, operated respectively by a resilient arm 76 carried by the toggle link 43 and by a lever 77 co-operating with the rollers 24, control indicators showing that the latch is engaged and that the table has reached its indexed position respectively.

I claim:

1. In combination with an indexing table and a fixed support on which the said indexing table is rotatably mounted, a latching device for holding said table in any one of a plurality of indexed positions, said latching device comprising a plurality of cylindrical buttons projecting axially from said table, a latch lever, pivotal mounting means for said latch lever on said support, means to move said latch lever about its pivot, said latch lever being shaped to define a notch adapted to receive any one of said buttons, and thereby hold the table against rotation, and two rollers mounted on the latch lever one on each side of the notch and having adjacent portions of their peripheries extending into the notch, the spacing between the said rollers being slightly less than the diameter of any one of said buttons and the latch lever, when engaging a button, having the axis of the said button substantially on a line joining the centers of the rollers, whereby the button is in interference contact with the rollers when the latch is engaged.

2. The combination of claim 1, and further comprising spring means urging the latch lever to a position in which a button is engaged in the notch, a roller follower mounted on the latch lever, a Geneva mechanism comprising a driving member and a driven member, a rotatable assembly comprising a rotary cam and the driving member of the Geneva mechanism, said roller follower engaging said cam, spur gear mechanism and a friction clutch connecting the driven member of the Geneva mechanism to the table, and driving means for said rotatable assembly.

3. The combination of claim 1, wherein said latch lever further includes link means adapted to cooperate with indicator control means to indicate any position to which the table is indexed.

4. The combination of claim 3, wherein the indicator control means include switch means.

References Cited UNITED STATES PATENTS 520,362 5/ 1894 Jennings. 1,985,477 12/1934 Wolf 74-820 X 2,481,642 9/ 1949 Bohmer et al. 2,934,977 5/1960 Wildhaber 74-822 2,968,973 1/1961 Mead 74-822 3,226,999 1/ 1966 Allison 74--813 X FRED C. MATTERN, JR., Primary Examiner.

F. D. SHOEMAKER, Assistant Examiner. 

